Typically, when a calling endpoint device desires to establish a call session with an endpoint device of a called party, the calling endpoint device goes off-hook and a call setup signaling message is generated at a local end office (e.g., an SSP). In some packet-based telephony networks, the call setup signaling message is directed toward the called endpoint device and is intercepted by a session border controller (SBC). After receiving the call setup message, the SBC generates a second call setup message (i.e., a second call leg) that is directed toward the called endpoint device. Thus, the SBC is acting as a back-to-back user agent by establishing and coordinating separate call signaling legs. Once the call signaling process is completed, the SBC then establishes the media path for communicating the media traffic between the two endpoint devices. This process usually involves identifying and assigning media routers positioned between the SBC and each endpoint that can handle the media packets. In some instances, the SBC accomplishes this task by performing a route lookup and media access control (MAC) address resolution for one or more media routers.
At present, the route lookup and the MAC address resolution are performed after the packets are received by SBC on a redirect stream and after the call signaling stage is completed. However, performing the route lookup and MAC address resolution after call signaling process is completed can lead to some problems, such as the call session not having any audio if the route lookup/MAC address resolution fails. The problem may also persist if the original caller repeatedly attempts to make calls to the same failed destination. Since the call was successfully established in the signaling stage, the end office that sent the call to the SBC is effectively prevented from searching for another provider that can provide successful media routing since the end office does not detect any call setup problems.
Accordingly, a need exists for improved methods, systems, and computer readable media for verifying the availability of an IP media router during a call setup.